A typical fuel cell includes a cell stack configured by a number of power generation cells, which are stacked together. A conventional power generation cell will hereafter be described with reference to FIGS. 23 to 25. As illustrated in FIG. 23, an electrode structure 15 is mounted in a joint portion between a pair of frames 13, 14. The electrode structure 15 is configured by a solid electrolyte membrane 16, an anode-side electrode catalyst layer 17, and a cathode-side electrode catalyst layer 18. The outer periphery of the solid electrolyte membrane 16 is clamped between the frames 13, 14. The anode-side electrode catalyst layer 17 is stacked on the top surface of the electrolyte membrane 16. The cathode-side electrode catalyst layer 18 is laid on the bottom surface of the electrolyte membrane 16. An anode-side gas diffusion layer 19 is laid on the top surface of the electrode catalyst layer 17. A cathode-side gas diffusion layer 20 is laid on the bottom surface of the electrode catalyst layer 18. An anode-side gas passage forming member 21 is laid on the top surface of the gas diffusion layer 19. A cathode-side gas passage forming member 22 is formed on the bottom surface of the gas diffusion layer 20.
As illustrated in FIG. 24, the gas passage forming member 21 (22) is formed by a metal lath. In the metal lath, a number of hexagonal ring portions 21a (22a) are formed in a serpentine manner. A through hole 21b (22b) is formed in each of the ring portions 21a (22a). Fuel gas (oxidization gas) flows in a gas passage formed by the ring portions 21a (22a) and the through holes 21b (22b). FIG. 25 is an enlarged view showing a portion of the gas passage forming member 21, 22.
With reference to FIG. 23, a fuel gas supply passage M1 and a fuel gas discharging passage M2 are formed in the frames 13, 14. The fuel gas supply passage M1 is a passage through which hydrogen gas as fuel gas is supplied to a gas passage in the anode-side gas passage forming member 21. The fuel gas discharging passage M2 is a passage through which the fuel gas that has passed through the gas passage of the gas passage forming member 21, which is fuel off-gas, is discharged to the exterior. An oxidization gas supply passage and an oxidization gas discharging passage are formed in the frames 13, 14. The oxidization gas supply passage is located at the backside of the sheet as viewed in FIG. 23. The oxidization gas supply passage is a passage through which the air as oxidization gas is supplied to a gas passage in the cathode-side gas passage forming member 22. The oxidization gas discharging passage is located at the front side of the sheet as viewed in FIG. 23. The oxidization gas discharging passage is a passage through which the oxidization gas that has passed through the gas passage of the gas passage forming member 22, which is oxidization off-gas, is discharged to the exterior.
Hydrogen gas is supplied from a non-illustrated hydrogen gas supply source to the gas passage forming member 21 through the fuel gas supply passage M1 along the gas flow direction P indicated by the arrow in FIG. 23. Also, the air is supplied from a non-illustrated air supply source to the gas passage forming member 22. This causes an electrochemical reaction to produce power in the power generation cell.
Patent Document 1 discloses a fuel cell similar to the configuration shown in FIG. 23.
As a conventional fuel cell, a fuel cell disclosed in Patent Document 2 has been proposed. As shown in FIG. 26, the fuel cell has a separator base plate 73, which is arranged between an air-electrode-side collector 71 and a fuel-electrode-side collector 72. With reference to FIG. 27, the air-electrode-side collector 71 is held in contact with a solid electrolyte membrane 74. The air-electrode-side collector 71 is configured by bottom portions 71a held in contact with an air-electrode-side diffusion layer 75 having a water repellent layer, top portions 71b held in contact with the separator base plate 73, and grid-like openings 71c formed in the bottom portions 71a and the top portions 71b. Oxidization gas is supplied to the air-electrode-side diffusion layer 75 via a gas passage formed in the air-electrode-side collector 71. Water produced in the gas passage through power generation flows downstream from the gas passage.
As another conventional fuel cell, a fuel cell disclosed in Patent Document 3 has been proposed. As illustrated in FIG. 28, in the fuel cell, an electrolyte-side gas supply passage 83 is formed between a gas diffusion layer 81 held in contact with an electrode structure 15 and a water drainage layer 82 formed by a porous body. A water drainage passage 85 is formed in a surface 84 of the water drainage layer 82. Specific suction means (not shown) is arranged in the water drainage passage 85. The water drainage passage 85 causes water generated in the gas supply passage 83 through power generation to permeate through slits formed in the water drainage layer 82 and introduces the water to the water drainage passage 85.
A fuel cell disclosed in Patent Document 4 has also been proposed as a conventional fuel cell. A water drainage tube having a through hole formed in a side wall, through which generated water permeates, is embedded in a cathode-side catalyst layer. A water drainage pump is connected to the water drainage tube through a line. The water drainage pump depressurizes the interior of the water drainage tube and thus draws the generated water from the cathode-side catalyst layer into the water drainage tube. The water is then directed to the exterior of a membrane-electrode assembly.